Fuel-injection valve

ABSTRACT

A fuel injector ( 1 ), especially for the direct injection of fuel into a combustion chamber of an internal combustion engine has an actuator ( 10 ) which is in operative connection with a valve needle ( 3 ), the valve needle ( 3 ) having a valve-closure member ( 4 ) at its spray-off end, which cooperates to form a sealing seat together with a valve seat surface ( 6 ) which is formed on a valve seat element ( 5 ). Valve-closure member ( 4 ) reaches through a swirl element ( 32 ) which is positioned on a flow-supply side end face ( 35 ) of valve seat element ( 5 ), swirl channels ( 33 ) being formed in swirl element ( 32 ). The valve seat element ( 5 ) has a ring-shaped elevation ( 36 ) on the flow-supply side end face ( 35 ) facing the swirl element ( 32 ).

BACKGROUND INFORMATION

[0001] The present invention is based on a fuel injector of the type setforth in the main claim.

[0002] A fuel injector is known from DE 197 36 682 A1 for directinjection of fuel into the combustion chamber of a mixture-compressing,internal combustion engine having externally supplied ignition, whichhas a guide and seating region at the downstream end of the fuelinjector formed by three disk-shaped elements. In this connection, aswirl element is embedded between a guide element and a valve seatelement. The guide element is used for guiding an axially movable valveneedle reaching through it, while a valve closing section of the valveneedle acts together with a valve seat surface of the valve seatelement. The swirl element has an inner opening region having severalswirl channels which are not in communication with the outercircumference of the swirl element. The entire opening region extendscompletely over the axial thickness of the swirl element.

[0003] It is particularly disadvantageous in the fuel injector knownfrom the above-named document that gaps are created, during assembly ofthe swirl element, between the swirl element and the guide element, aswell as between the swirl element and the valve seat element. Thisalters the metering cross section, whereby the disoersion of the staticflow through the fuel injector is increased. This has a negative effecton the operation of the fuel injector because of differences in themetered fuel quantity per injection cycle.

SUMMARY OF THE INVENTION

[0004] By comparison, the fuel injector according to the presentinvention, having the characteristic features of the main claim, has theadvantage that the valve seat element has a ring-shaped elevation on itsend face on the fuel supply side facing the swirl element, and thiselevation is higher than the unevenness of the surfaces of the valveseat element and the swirl element caused by manufacturing processes.Because of this, the gaps between the valve seat element and the swirlelement arising from the assembly and subsequent heating during theoperation of the fuel injector are reduced to a value fixed by theheight of the ring-shaped elevation, which may compensated for bysetting the static flow-through using other components, such as asetting device in the system of fuel supply.

[0005] Advantageous further developments of the fuel injector specifiedin the main claim are rendered possible by the measures given in thedependent claims.

[0006] In this context, of particular advantage is the design of a ringsurface on the ring-shaped elevation, which makes the component partless sensitive to manufacturing tolerances.

[0007] It is also of advantage that the swirl element is clamped inbetween the guide element and the valve seat element during assembly,and therefore temperature changes during the operation of the fuelinjector have no effect on the gap width or the quantity of meteredfuel.

[0008] The fuel channels of the guide element are advantageouslyarranged in such a way that the fuel may run without hindrance andwithout disturbing throttle effects into the swirl channels and flow tothe sealing seat.

[0009] The design of a swirl chamber is also of advantage, whose volumeis selected, depending on the requirements, so that throttle effects maybe eliminated.

[0010] The wedge-shaped areas at the end face of the valve seat element,bordering on the ring-shaped elevation, are easy to manufacture and,depending on the requirements, may be provided with any angles relativeto a horizontal plane of reference.

[0011] The ring-shaped elevation may also be made in the shape of a ringwhich is attached to the end face of the valve seat element. Theadvantage of this embodiment variant is that one may take over thestandard valve seat element without change.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Exemplary embodiments of the invention are explained in greaterdetail in the following description and are shown simplified in thedrawings. The figures show:

[0013]FIG. 1 a schematic section through a first exemplary embodiment ofa fuel injector according to the present invention,

[0014]FIG. 2A a schematic partial section through a first exemplaryembodiment of a fuel injector according to the present invention inregion IIA in FIG. 1,

[0015]FIG. 2B an enlarged view of the valve seat element of the firstexemplary embodiment of the fuel injector according to the presentinvention shown in FIG. 2A.

[0016]FIG. 2C a view of a second exemplary embodiment of the fuelinjector according to the present invention in the same region as inFIG. 2B, and

[0017]FIG. 2D a schematic view of the swirl element of a fuel injectoraccording to the present invention from opposite to the flow directionof the fuel.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0018] Before exemplary embodiments of a fuel injector according to thepresent invention are described more precisely with reference to FIGS.2A through 2D, to understand the invention better, fuel injector 1 shallfirst of all be briefly explained in an overall representation withrespect to its important components with the aid of FIG. 1.

[0019] Fuel injector 1 is designed in the form of an injector forfuel-injection systems of mixture-compressing internal combustionengines having externally supplied ignition. Fuel injector 1 isparticularly suitable for directly injecting fuel into a combustionchamber (not illustrated) of an internal combustion engine.

[0020] Fuel injector 1 includes a nozzle body 2, in which a valve needle3 is positioned. Valve needle 3 is connected in operative connection toa valve-closure member 4 that cooperates with a valve-seat surface 6,arranged on a valve-seat member 5, to form a sealing seat. Fuel injector1 in the exemplary embodiment is an inwardly opening fuel injector 1which has a spray-discharge opening 7. Nozzle body 2 is sealed fromexternal pole 9 of a magnetic coil 10 by a seal 8. Magnetic coil 10 isencapsulated in a coil housing 11 and wound on a bobbin 12 which liesadjacent to an internal pole 13 of magnetic coil 10. Internal pole 13and external pole 9 are separated from each other by a gap and aresupported on a connecting component 29. Magnetic coil 10 is energizedvia an electric line 19 by an electric current which can be supplied viaan electrical plug-in contact 17. Plug-in contact 17 is enclosed in aplastic jacket 18, which may be sprayed onto internal pole 13.

[0021] Valve needle 3 is guided in a valve needle guide 14, which isdesigned as a disk. A paired adjustment disk 15 is used to adjust the(valve) lift. An armature 20 is on the other side of adjustment disk 15.It is connected by force-locking to valve needle 3 via a first flange21, and valve needle 3 is connected to first flange 21 by a welded seam22. Braced against valve needle 21 is a return spring 23 which, in thepresent design of fuel injector 1, is prestressed by a sleeve 24.

[0022] A second flange 31, which is connected to valve needle 3 via awelded seam 33, is used as lower armature stop. An elastic intermediatering 32, which lies upon second flange 31, avoids bounce when fuelinjector 1 is closed.

[0023] Fuel channels 30 a through 30 c run through valve needle guide14, armature 20 and valve seat member 5, which guide the fuel, suppliedvia central fuel supply 16 and filtered by a filter element 25, tospray-discharge opening 7. Fuel injector 1 is sealed by seal 28 from afuel line (not shown).

[0024] In the neutral position of fuel injector 1, return spring 23 actsupon armature 20 counter to its lift direction in such a way thatvalve-closure member 4 is retained in sealing contact against valve seat6. Upon excitation of magnetic coil 10, the latter generates a magneticfield which moves armature 20 in the lift direction, counter to thespring force of return spring 23, the lift being predefined by a workinggap 27 existing in the neutral position between internal pole 12 andarmature 20. Armature 20 also carries along in the lift direction flange21, which is welded to valve needle 3. Valve-closure member 4, beingconnected to valve needle 3, lifts off from valve seat surface 6, andfuel guided via fuel channels 30 a through 30 c to spray-dischargeopening 7 is sprayed off.

[0025] When the coil current is switched off, after sufficient decay ofthe magnetic field, armature 20 falls away from internal pole 13 becauseof the pressure of return spring 23, whereupon flange 21, beingoperatively connected to valve needle 3, moves in a direction counter tothe lift direction. Thereby valve needle 3 is moved in the samedirection in which valve-closing body 4 sets down upon valve seatsurface 6, and fuel injector 1 is closed.

[0026] In an extract cross section, FIG. 2A shows the spray-off end offuel injector 1 according to the present invention shown in FIG. 1. Thesection shown in FIG. 2A is designated in FIG. 1 as IIA. Here,components identical to those in FIG. 1 are marked with the samereference numerals.

[0027] The spray-off end of fuel injector 1 according to the presentinvention shown in FIG. 2A includes a valve seat element 5 which has aring-shaped elevation 36 on a fuel-supply side end face 35. An outflowopening 7 is formed in valve seat element 5. Valve seat element 5 formsa sealing seat together with valve seat surface 6 attached to it as wellas with valve-closure member 4, which is a part of valve needle 3. Inthis connection, valve needle 3 reaches through a guide element 31 aswell as a swirl element 32. Swirl element 32, in this situation, ispositioned between guide element 31 and valve seat element 5. Valve seatelement 5 is connected, via a welded seam 34, to swirl element 32 and toguide element 31. The connecting takes place preferably underprestressing, so that swirl element 32 takes up a position, relative tovalve seat element 5, which is not changeable any more by later heatingduring the operation of fuel injector 1 or by the lift movement of valveneedle 3.

[0028] Guide element 31 has fuel channels 30 c which correspond to swirlchannels 33 formed in swirl element 32.

[0029] Swirl element 32 is preferably formed disk-shaped at constantthickness, and lies on the fuel-supply side of end face 35 of valve seatelement 5. Because of ring-shaped elevation 36, unevennesses due tomanufacturing technology of swirl element 32 as well as of fuel-supplyside end face 35 of valve seat element 5 are reduced to a gap 40 havinga defined width. The width of gap 40 between valve seat element 5 andswirl element 32 may here amount to about 7 μm. The diameter ofring-shaped elevation 36 is selected in this case so that it intersectsswirl channels 33 of swirl element 32. Elevation 36 may also be formedto be partially ring-shaped, and interrupted in the area of swirlchannels 33. The diameter may here be 3.0 mm, for example. Ring-shapedelevation 36 may either be produced as one piece with valve seat element5 by slanting fuel-supply side end face 35, a wedge-shaped surface 38being formed, which drops off towards an outer side 37 of valve seatelement 5. However, it is also possible to produce ring-shaped elevation36 by positioning a ring-shaped structure on valve seat element 5. Inthat case, ring-shaped elevation 36 is connected to valve seat element 5by soldering or welding.

[0030] When fuel injector 1 is operated, valve needle 3 is moved counterto a flow direction of the fuel, whereby valve-closure member 4 liftsoff from valve seat surface 6, and fuel is sprayed off through fuelchannels 30 c, swirl channels 33 and spray-off opening 7.

[0031] To make the measure according to the present invention clearer,FIG. 2B shows in an enlargement valve seat element 5 of the firstexemplary embodiment shown in FIG. 2A.

[0032] To clarify ring-shaped elevation 36, two broken lines A and B areintroduced in FIG. 2B. Ring-shaped elevation 36 is here illustratedexaggeratedly high. Wedge-shaped surface 38 becomes lower towardsradially outer region 37 of valve seat element 5 by about 7 μm over thediameter of valve seat element 5, which is made clear by the distancebetween lines A and B in FIG. 2B. The form of valve seat surface 6 aswell as downstream structures such as spray-off opening 7 are notchanged by the measure according to the present invention.

[0033] In the same view as in FIG. 2B, FIG. 2C shows a further exemplaryembodiment of valve seat element 5 of a fuel injector 1 embodiedaccording to the present invention.

[0034] In contrast to FIG. 2B, ring-shaped elevation 36, which isdeveloped in FIG. 2B without significant radial extension, that is,edge-shaped because of wedge-shaped surface 38 bordering on inclinedvalve seat surface 6, is designed in the present second exemplaryembodiment as ring-shaped elevation 36 having a ring surface 41, whichlies against swirl element 32 in a planar manner. The radial expansionof ring surface 41 may in this instance be 0.2 to 0.4 mm, for example.The advantage of a planar stamping of ring-shaped elevation 36 is thatit makes for an improved seating against the swirl element, so thatmanufacturing tolerances do not lead to an increase in disoersion of thestatic flow-through, as would be possible, under certain circumstances,in the case of a sort of linear contact surface as in the firstexemplary embodiment, since even in the case of small unevennesses, newgaps are created between ring-shaped elevation 36 of valve seat element6 and swirl element 32.

[0035]FIG. 2D shows a top view of swirl element 32 having swirl channels33, which is penetrated by valve-closure member 4. Ring-shaped elevation36 of valve seat element 5 is here projected on swirl element 32. Inthis context, the outermost and the innermost circular line indicate theradial extension of ring-shaped elevation 36, shown in FIG. 2C by ringsurface 41.

[0036] Between swirl channels 33 and valve-closure member 4 a swirlchamber 39 is formed. In this connection, the volume of swirl chamber 39may be selected, according to the requirements on fuel injector 1 insuch a way that either intended throttle effects appear because of asmall diameter, or the throttle effects are completely eliminated by agreater volume of swirl chamber 39. The volume of swirl chamber 39, hasto be dimensioned in any case so that the swirl flow generated by swirlchannels 33 in swirl element 32 remains homogeneous and is not broughtto a standstill even during the idle time between two injection cyclesof fuel injector 1, since the injection properties would otherwise beinfluenced negatively.

[0037] According to the present invention, in the embodiment describedabove of valve seat element 5 of fuel injector 1, it may be achievedthat gap 40 caused by unevennesses due to the manufacturing process,present between swirl element 32 and valve seat element 5, may beeliminated to the extent that a constant width of gap 40 is attained,and the increase in flow-through conditioned on this is compensated forby a suitable setting of the static flow-through in the system of fuelsupply. As a result, overall only a very slight disoersion of the staticflow-through still appears.

[0038] The present invention is not limited to the illustrated exemplaryembodiment, and may also be used, for example, for equipment havingother swirl elements 32 having more or fewer swirl channels 33 as wellas for any embodiments of fuel injectors 1 having any actuators 10.

What is claimed is:
 1. A fuel injector (1), especially for the directinjection of fuel into a combustion chamber of an internal combustionengine, having an actuator (10) which is in operative connection with avalve needle (3), the valve needle (3) having a valve-closure member (4)at its spray-off end which cooperates to form a sealing seat togetherwith a valve seat surface (6) which is formed on a valve seat element(5), and the valve-closure member (4) reaches through a swirl element(32) which is positioned at a flow-supply side end face (35) of thevalve seat element (5), the swirl channels (33) being developed in theswirl element (32), wherein the valve seat element (5) having aring-shaped or partially ring-shaped elevation (36) on the flow-supplyside end face (35) facing the swirl element (32).
 2. The fuel injectoras recited in claim 1, wherein the ring-shaped elevation (36) isdeveloped as one piece with the valve seat element (5) or is connectedto it.
 3. The method as recited in claim 1 or 2, wherein the ring-shapedelevation (36) has a ring surface (41) which lies against the swirlelement (32) in a planar manner.
 4. The fuel injector as recited in oneof claims 1 through 3, wherein the ring-shaped elevation (36) issurrounded at a radially outer side (37) by a wedge-shaped area (38). 5.The fuel injector as recited in claim 4, wherein the wedge-shaped area(38) falls off radially outwards.
 6. The fuel injector as recited inclaim 2, wherein the ring-shaped elevation (36) is connected to theflow-supply side end face (35) by welding, soldering or similar methods.7. The fuel injector as recited in one of claims 1 through 6, whereinthe swirl element (32) is positioned between a guide element (31) andthe valve seat element (5).
 8. The fuel injector as recited in one ofclaims 1 through 7, wherein the guide element (31) has fuel channels (30c) which correspond to the swirl channels (33) of swirl element (32). 9.The fuel injector as recited in one of claims 1 through 8, wherein theguide element (31) and the swirl element (32) are connected to the valveseat element (5) by a welded seam (34).
 10. The fuel injector as definedin one of claims 1 through 9, wherein between the swirl element (32) andthe valve-closure member (4) a swirl chamber (39) is formed.